Diffusion of platinum and molybdenum in Ni and Ni3Al

Diffusion coefficients (m(2)/s) of Pt and Mo in Ni and Ni3Al(gamma') were determined by Hall's method using diffusion couples. Their temperature dependences are as follows: D-Pt(gamma') = 7.8 x 10(-4) exp{-323(kJ/mol)/RT} and D-Mo(gamma') = 2.3 x 10(2) exp{-493(kJ/mol)/RT}D-Pt(Ni) = 3.5 x 10(-5) exp{-280(kJ/mol)/RT} and D-Mo(Ni) = 1.3 x 10(-4) exp{-283(kJ/mol)/RT}. From this study, the following mechanism of diffusion in Ni3Al is proposed; the diffusion of Pt atoms which substitute for Ni-sites (alpha) occurs mainly by random jumps from alpha- to alpha-sites through the vacancies on alpha-sites. The Mo atoms which substitute for Al-sites (beta) jump to alpha-sites with a local disordering, and then they diffuse randomly through alpha-sites.